DescriptionThis dissertation examines select topics in the syntax of non-finite clauses in Mapudungun, an isolate spoken in Chile and Argentina. Much of the data presented was collected from extensive fieldwork in Chile carried out by the author. I first defend Baker’s theory that the diverse infinitival markers -n, -el, -t, and -m are allomorphs of a single morpheme, Inf. In the process, I formulate a theory of wh-agreement on which this is analogous to subject and object agreement and propose that extraction of a non-subject and of an oblique trigger the allomorphs -el and -m, respectively. I also characterize clauses with the non-finite morphemes -lu and -wma as active and passive participles, respectively. Secondly, I argue that Mapudungun infinitival clauses are CPs, despite having the appearance of possessed nominals. Thirdly, I argue for a characterization of the verbal morpheme -a, often analyzed as a future tense, as a future modal. Lastly, I describe the distribution of this future modal morpheme -a in Mapudungun complement clauses, identifying the classes of predicates which require -a, allow but do not require -a, and ban -a in their clausal complement. I argue that emotive and propositional predicates license identical complements, and develop a semantic theory of complement clause selection which accounts for these complementation facts. In particular, I identify the selectional restrictions of a predicate with its argument structure, containing individual thematic roles, and propose that predicates themselves transmit the features they select for to their complements via the individual thematic role assigned to them. This selection-for-individual-roles theory endorses a coherence licensing condition: a clause is licensed as complement if it is compatible with the selectional restrictions of a predicate. Thus, to be licensed, a complement clause is only required to be compatible with the specification imparted by the predicate; it is not required to satisfy these selectional restrictions of the predicate.